PREFACE 
The U. S. Naval Civil Engineering Laboratory is conducting a research program 
to determine the effects of the deep-ocean environment on materials. This research 
will be of great value in establishing the best materials to be used in deep-ocean con- 
struction in the Navy's conquest of "inner space.” 
A Submersible Test Unit (STU) was designed, on which many test specimens can 
be mounted. The STU can be lowered to the ocean bottom and left for long periods 
of exposure. Planned exposures range from 4 to 48 months at depths from 2,500 to 
18,000 feet. 
Thus far, two deep-ocean test sites have been selected. Test Site | (nominal 
depth of 6,000 feet) is approximately 81 nautical miles southwest of Port Hueneme, 
California. Test Site II (nominal depth of 2,500 feet) is 75 nautical miles west of 
Port Hueneme. Additional test sites at depths of 12,000 and 18,000 feet may be 
chosen. This report deals with STU I-1, in place for 3 years at a depth of 5,300 feet. 
